The Pfitzner–Moffatt oxidation, sometimes referred to as simply the Moffatt oxidation, is a

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and break ...

for the

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

of primary and secondary alcohols to

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

s and

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

s, respectively. The oxidant is a combination of

dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...

(DMSO) and

dicyclohexylcarbodiimide ''N'',''N''′-Dicyclohexylcarbodiimide (DCC or DCCD) is an organic compound with the chemical formula (C6H11N)2C. It is a waxy white solid with a sweet odor. Its primary use is to couple amino acids during artificial peptide synthesis. The lo ...

(DCC). The reaction was first reported by J. Moffatt and his student K. Pfitzner in 1963.

Stoichiometry and mechanism

The reaction requires one equivalent each of the diimide, which is the dehydrating agent, and the sulfoxide, the oxidant: :(CH₃)₂SO + (CyN)₂C + R₂CHOH → (CH₃)₂S + (CyNH)₂CO + R₂C=O Typically the sulfoxide and diimide are used in excess. The reaction cogenerates

dimethyl sulfide Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. Dimethyl sulfide is a flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from co ...

and a

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

Dicyclohexylurea Dicyclohexylurea is an organic compound, specifically, a urea. It is the byproduct of the reaction of dicyclohexylcarbodiimide with amines or alcohols. It may be prepared by the reaction of cyclohexylamine Cyclohexylamine is an organic compound, ...

((CyNH)₂CO) can be difficult to remove from the product. In terms of mechanism, the reaction is proposed to involve the intermediary of an

sulfonium In organic chemistry, a sulfonium ion, also known as sulphonium ion or sulfanium ion, is a positively-charged ion (a "cation") featuring three organic substituents attached to sulfur. These organosulfur compounds have the formula . Together wit ...

group, formed by a reaction between DSMO and the carbodiimide. : Aktivierung des DMSO (Pfitzner-Moffatt)

This species is highly reactive and is attacked by the alcohol. Rearrangement give an alkoxysulfonium

ylide An ylide or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both ato ...

which decomposes to give dimethyl sulfide and the

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containin ...

compound. : Pfitzner-Moffatt Reaktionsmechanismus 1

This reaction has been largely displaced by the

Swern oxidation The Swern oxidation, named after Daniel Swern, is a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine. It is on ...

, which also uses DMSO as an oxidant in the presence of an electrophilic activator. Swern oxidations tend to give higher yields and simpler workup.Lee, T. V. ''Compr. Org. Synth.'' 1991, ''7'', 291–303. (Review)

References

{{reflist Organic oxidation reactions Name reactions

Stoichiometry and mechanism

See also

References